I want to ask why I can't buy a mobile phone with a credit card. There are several reasons why you can't use a credit card when buying a mobile phone:

1. Insufficient credit card limit: your credit card limit is insufficient to complete the payment. You can contact the credit card issuer to check the credit card limit and confirm whether it is necessary to increase the limit.

2. The credit card has expired: your credit card has expired, so you can't complete the payment. You can contact the credit card issuer to apply for a new credit card or renew the validity period of the credit card.

3. The credit card is frozen: Your credit card will be frozen due to arrears or illegal operations, which will make it impossible to complete the payment. You can contact the credit card issuer to check the status of the credit card and confirm whether it needs to be unfrozen.

4. Network problems: When you pay by credit card, you will encounter network problems, which will lead to payment failure. You can try to change the network environment or contact the credit card issuer to check the payment record and confirm whether the deduction has been made.